- Polycarbonate (PC) has a published lifespan of 10–20 years, but that number is only valid under specific conditions. Uncoated outdoor PC can fail in 2–5 years. Controlled indoor PC can last 25+ years.
- The three failure mechanisms that kill PC parts in service — UV photo-oxidation, thermal embrittlement, and Environmental Stress Cracking (ESC) — are all predictable and largely preventable at the design and material selection stage.
- Most premature PC failures are not material failures. They are specification failures: wrong grade for the environment, residual stress locked in during moulding, or chemical incompatibility that was never audited.
- This guide gives engineering and procurement teams the technical framework to specify, validate, and procure polycarbonate components with a defensible lifespan prediction — not a guess.
1. Why Lifecycle Prediction Matters in Polycarbonate Engineering
A client in the German automotive sector recently posed a question that most procurement and engineering teams should ask more often: “Under real-world stress, when will this part actually fail?”
The question is not academic. In industrial manufacturing, a lifecycle prediction is a design input — it determines grade selection, surface treatment, processing parameters, and the inspection criteria you write into your supply agreement. Getting it wrong produces one of two outcomes:
- Over-specification: premium UV-stabilised grade, hard coat, and elevated processing controls on a part that lives in a sealed indoor enclosure. Unnecessary cost.
- Under-specification: standard optical-grade PC on an outdoor application, no UV coat, inadequate annealing. Part fails in 18 months. Warranty claim, field replacement, and reputational damage.
The general industry consensus — “polycarbonate lasts 10 to 20 years” — is a statistical average across all environments. It is not a specification. For engineering purposes, lifespan is a calculated output that depends on four variables:
- Environmental stressors (UV dose, temperature, humidity, chemical exposure)
- Material grade and additives (UV stabilisers, heat stabilisers, impact modifiers)
- Processing quality (residual stress, surface condition, dimensional accuracy)
- Design geometry (stress concentrators, wall thickness, load distribution)
This guide provides the framework to evaluate all four.
2. How Polycarbonate Degrades: The Three Primary Mechanisms
Understanding degradation mechanisms is not academic background — it is the basis for selecting the correct grade, specifying the correct post-processing, and writing a meaningful acceptance test. There are three primary mechanisms that drive end-of-life in polycarbonate components.
2.1 Photo-Oxidation (UV Degradation)
What happens at the molecular level:
UV radiation in the 290–400 nm wavelength range has sufficient photon energy to break the ester and carbonate linkages in the PC polymer backbone — a process called chain scission. As molecular weight decreases, two things happen simultaneously:
- Yellowing (chromophore formation): Oxidation products form conjugated double bonds that absorb visible light in the blue end of the spectrum, causing the characteristic yellow-brown discolouration visible on aged PC.
- Embrittlement: Lower molecular weight reduces impact energy absorption. A PC part that was initially rated for high-impact applications can become brittle enough to fracture at low impact loads after sustained UV exposure.
Why this matters for procurement: UV degradation begins immediately on first exposure and progresses continuously. There is no threshold dose below which it is safe to ignore — there is only a rate, which is controlled by:
- UV stabiliser content in the grade (hindered amine light stabilisers / HALS; UV absorbers)
- Presence and quality of a co-extruded or applied UV-protective coating
- Cumulative UV dose in the deployment environment (measured in kJ/m² or MJ/m²)
Key specification question: “Does the grade datasheet report UV stability data (e.g., ΔE colour shift per 1,000 hours of Xenon arc exposure to ISO 4892-2)?”
2.2 Thermal Degradation and the Glass Transition Temperature
The Tg boundary:
Polycarbonate has a glass transition temperature (Tg) of approximately 147°C. Below Tg, the polymer is in its glassy state — dimensionally stable, high modulus, predictable performance. Above Tg, it transitions to a rubbery state — dimensional stability is lost.
The engineering implication is not at Tg — it is well below it:
Continuous service temperatures above 100°C accelerate the following:
| Thermal effect | Mechanism | Engineering consequence |
|---|---|---|
| Thermal oxidation | Oxygen-mediated chain scission at elevated temperature | Accelerated embrittlement; synergistic with UV |
| Stress relaxation | Frozen-in moulding stresses redistribute under heat | Warping, dimensional drift, loss of fit/function |
| Crazing | Combined thermal cycling and residual stress | Network of fine surface micro-cracks; structural precursor to fracture |
| Hydrolysis (with moisture) | Ester bond cleavage in presence of water at elevated temperature | Molecular weight reduction; surface degradation |
Thermal cycling (repeated excursions between temperature extremes) is often more damaging than sustained elevated temperature because it drives repeated expansion/contraction cycles that progressively develop micro-crack networks in areas of stress concentration.
Key specification question: “What is the maximum continuous-use temperature and peak excursion temperature for this application? Have you selected a heat-stabilised grade?”
2.3 Environmental Stress Cracking (ESC)
ESC is the most common cause of premature field failure in polycarbonate components, and the least well understood by procurement and non-specialist engineering teams.
Mechanism:
ESC occurs when a polymer under mechanical stress — including residual moulding stress — comes into contact with a chemical agent that reduces the surface energy of the polymer, allowing crack propagation at stress levels well below the nominal fracture strength. The chemical is not a solvent (it does not dissolve the PC) — it acts as a crack initiation catalyst.
The result is sudden, brittle fracture — often with no preceding visible warning signs — at loads the part should be able to tolerate comfortably.
Common ESC-causing agents for polycarbonate:
| Chemical class | Examples | Engineering context |
|---|---|---|
| Ketones | Acetone, MEK | Cleaning agents, adhesive solvents |
| Esters | Ethyl acetate, butyl acetate | Paint and coating solvents |
| Aromatic hydrocarbons | Toluene, xylene | Industrial cleaning, degreasers |
| Amines | Ammonia-based cleaners | Industrial cleaning products |
| Some alcohols (high concentration) | Isopropyl alcohol >30% | Surface cleaning; depends on stress state |
| Fuels (some) | Certain hydraulic fluids, fuel blends | Automotive and industrial environments |
Why it fails without warning: A PC part with locked-in moulding residual stress is in a permanently stressed state even when carrying no external load. When it contacts an ESC-active chemical, the crack propagates rapidly through the residual stress field. The apparent cause is the chemical contact, but the root cause is the residual stress — which was created during the moulding process.
Key specification question: “Has a chemical compatibility audit been conducted for all agents the part will encounter in service, cleaning, assembly, and maintenance — not just the primary process fluid?”
3. Lifespan Variable Matrix: Environment vs. Expected Life
The table below provides working lifespan estimates for polycarbonate across the environments most relevant to industrial and commercial engineering applications. These are engineering guidance values based on established degradation models and industry experience — not guarantees. Actual service life depends on specific grade, processing quality, and load conditions.
Table 1: Polycarbonate Life Expectancy by Environment
| Environment | Estimated Lifespan | Primary Failure Mode | Minimum Grade Requirement | Mitigation Strategy |
|---|---|---|---|---|
| Controlled indoor (sealed, HVAC) | 20–25+ years | Surface scratching; minimal structural degradation | Standard PC (e.g., Makrolon 2405) | Soft-cloth cleaning protocol; avoid ESC-active cleaning agents |
| Covered outdoor / indirect UV | 12–18 years | Gradual yellowing; moderate impact reduction | UV-stabilised PC | Annual UV-protective treatment; ESC chemical audit |
| Outdoor with UV coat (quality applied) | 10–15 years | Coat delamination then yellowing; slow impact reduction | UV-stabilised PC + applied siloxane hard coat | Periodic coat inspection; recoat at first sign of adhesion failure |
| Outdoor uncoated | 2–5 years | Severe brittleness; rapid yellowing; surface crazing | Not recommended for structural use | Redesign: apply UV coat or change material to UV-stable PMMA or ASA |
| High-temperature industrial (continuous >100°C) | 5–10 years | Thermal embrittlement; warping; crazing | Heat-stabilised PC grade | Specify heat-stabilised grade; design for thermal expansion; minimise residual stress in moulding |
| Chemically active environment | Weeks to 20+ years (application-dependent) | ESC → sudden brittle fracture | Grade + chemical compatibility analysis required | Mandatory chemical audit; hard coat or change to PEEK/PEI for severe environments |
| Humid/condensing (tropical, marine) | 10–18 years | Hydrolysis at surface; reduced impact strength | UV + hydrolysis-stabilised grade | Material selection review; surface coating; drainage by design |
| Cyclic UV + thermal + moisture (most outdoor) | 8–12 years | Combined degradation; synergistic acceleration | UV-stabilised PC + hard coat + heat stabiliser | Use Xenon arc accelerated ageing test (ISO 4892-2) to validate before production commit |
How to use this table:
This is a starting point for material specification — not a warranty. If your application falls into the bottom three rows, commission an accelerated ageing test (Section 8) before committing to polycarbonate. If it falls in the top two rows, standard grade PC with a defined cleaning protocol is typically sufficient.
4. Material Grade Selection: What the Datasheet Doesn’t Tell You
Specifying “polycarbonate” on a drawing is the equivalent of specifying “steel” without a grade, condition, or heat treatment. The grade determines almost everything about real-world performance.
4.1 Grade Categories Relevant to Engineering Applications
| Grade category | Typical designations | Key additives | Best for | Avoid for |
|---|---|---|---|---|
| Standard / general purpose | Makrolon 2405, Lexan 101 | None (or minimal) | Indoor structural, optical enclosures | Outdoor, high-temperature, chemical exposure |
| UV-stabilised | Makrolon 2605 UV, Lexan 143 UV | HALS + UV absorbers (co-extruded layer or compounded) | Outdoor glazing, covers, housings | Direct chemical exposure without coat |
| Optical grade | Makrolon OD2015, Lexan LS2 | Optical clarity additives; minimal stabilisers | Lenses, light guides, display covers (indoor) | Outdoor UV; often lacks stabiliser package |
| Heat-stabilised | Makrolon 3108, Bayblend HI grades | Heat stabilisers; oxidation inhibitors | Engine bays, industrial controls, elevated-temperature enclosures | High-optical-clarity requirements |
| Glass-filled (PC-GF) | PC-GF10, PC-GF30 | Glass fibre reinforcement | Structural components, precision housings needing dimensional stability | Transparent applications; impact applications with crack propagation concern |
| PC/ABS blend | Bayblend T45, Cycoloy | Balanced toughness and processability | Automotive interior, consumer electronics housings | High-temperature, outdoor UV |
| Chemical-resistant grade | Makrolon RX2530, Lexan CXT | Modified backbone; reduced ESC sensitivity | Cleaning agent exposure, laboratory equipment, medical housings | Not a substitute for full chemical audit |
| Flame-retardant | Makrolon FR2010, Lexan FR530 | FR additives (typically UL 94 V-0 rated) | Electrical enclosures, railway interiors, data equipment | Optical applications; may affect clarity and impact performance |
4.2 The Grade Specification Mistake Most Often Made
Specifying optical grade for outdoor use is the most common and costly grade selection error. Optical-grade PC is formulated to maximise transmission clarity and minimise haze — it typically contains minimal UV stabilisers and chemical resistance additives. It will yellow and embrittle faster than a standard-grade UV-stabilised PC.
If you need both optical clarity and outdoor durability:
- Specify a UV-stabilised grade with documented UV stabiliser chemistry
- Or specify a standard UV-stabilised base material with a co-extruded UV-protective cap layer (the industry standard for glazing applications)
- Apply a siloxane-based hard coat — this provides both UV protection and scratch resistance
What to request from a supplier to confirm grade suitability:
| Data point | Why it matters | What to look for |
|---|---|---|
| UV stabiliser type and loading | Determines outdoor longevity | HALS + UV absorber combination; published ΔE at 1,000+ Xenon arc hours |
| Heat deflection temperature (HDT) | Confirms thermal headroom | HDT at 1.82 MPa (ISO 75-1) should exceed max service temperature by ≥ 20°C |
| Notched Izod / Charpy impact strength | Baseline impact resistance | Confirm against application load case; check aged vs. unaged values |
| ESC resistance data | Confirms compatibility with known chemical agents | Strain at failure in contact with test chemicals; published F50 ESC data |
| Flame classification | Required for electrical and transit applications | UL 94 rating (V-0, V-2, HB) and relevant wall thickness |
| Regulatory compliance | Medical, food contact, aerospace | FDA, EU 10/2011, REACH, RoHS as applicable |
5. Design and Processing Factors That Determine Real-World Life
Material grade accounts for perhaps 50% of a polycarbonate component’s service life. The other 50% is determined by how the part is designed and how it is manufactured. This is the section most often omitted from procurement specifications — and the most common source of premature field failure.
5.1 Residual Stress: The Silent Failure Driver
Residual stress in moulded polycarbonate is unavoidable — it is a consequence of the moulding process. The question is how much residual stress exists and whether it exceeds the threshold at which ESC or thermal cracking becomes a risk.
Sources of residual stress in injection-moulded PC:
| Source | Mechanism | Effect on service life |
|---|---|---|
| Over-packing | Excess injection pressure compresses polymer beyond the cavity; stress frozen in on cooling | High residual compressive/tensile stress; ESC risk elevated |
| Rapid cooling | Skin solidifies faster than core; differential contraction locked in | Surface tensile stress; crazing initiation sites |
| Gate location and design | Flow imbalance creates stress concentration near gate | Gate area most vulnerable to ESC and cracking |
| Insufficient cooling time | Part ejected before core fully solidified | Warping; internal stress redistribution in service |
| Incorrect barrel temperature | Over-heated PC undergoes partial thermal degradation in the barrel before the part is even made | Reduced molecular weight at point of manufacture |
How to mitigate residual stress:
- Annealing: Post-moulding heat treatment (typically 120–125°C for 1–4 hours, depending on wall thickness) allows molecular chains to relax and frozen-in stresses to partially relieve. Annealing does not eliminate residual stress but significantly reduces it. For ESC-sensitive applications, specify annealing as a mandatory post-processing step.
- Process optimisation: Request a moulding process record with pack pressure, injection speed, melt temperature, mould temperature, and cooling time. Any deviation from validated parameters should trigger a conformance review.
- Polarised light inspection: Residual stress in transparent PC can be visualised using a polarising filter. Parts with high stress show strong birefringence patterns. This is a rapid, non-destructive check that should be part of first article inspection for transparent structural PC components.
5.2 Surface Processing and Its Effect on Longevity
Polishing: Polycarbonate is frequently polished for optical clarity applications. Aggressive mechanical polishing (hard buffing compounds, excessive pressure) removes surface material non-uniformly, introduces micro-scratches that act as stress concentrators, and can partially melt the surface layer — creating a thin zone of high residual stress. Specify polishing method and compound; diamond paste with controlled pressure is preferred over aggressive buffing.
Machining: CNC-machined polycarbonate (common for prototype and low-volume precision components) has different residual stress characteristics to injection-moulded parts. Cutting forces introduce localised surface stress; incorrect tool geometry or excessive cutting speed can cause local thermal degradation. Post-machining annealing is recommended for dimensionally critical or ESC-sensitive machined PC parts.
Coating and surface treatment:
| Treatment | Purpose | Engineering notes |
|---|---|---|
| Siloxane hard coat (plasma or dip applied) | UV protection + scratch resistance | Industry standard for outdoor optical PC; verify adhesion by cross-cut test (ISO 2409) |
| Anti-fog coating | Condensation management | Applicable to automotive and PPE applications; verify chemical compatibility |
| Anti-static coating | ESD protection in electronics environments | Reduces particulate adhesion; verify conductivity spec |
| Physical vapour deposition (PVD) | Decorative or functional metalisation | Requires adhesion layer; not suitable for flexible parts |
| Primer + topcoat (wet paint) | Colour, protection | Ensure solvent in paint system is ESC-compatible with PC base; many common paint solvents cause ESC |
6. Chemical Compatibility: The Audit Your Procurement Process Needs
A chemical compatibility audit is a structured review of every chemical agent the part will encounter across its entire lifecycle — not just in primary service, but in assembly, maintenance, cleaning, storage, and disposal. Most procurement specifications address primary service fluid compatibility and ignore everything else.
6.1 The Lifecycle Chemical Exposure Map
For every polycarbonate component, map chemical exposure across each lifecycle stage:
| Lifecycle stage | Typical chemical exposures | Often missed? |
|---|---|---|
| Manufacturing / assembly | Adhesives, flux, cleaning solvents, mould release agents | Yes — rarely specified |
| Installation | Anti-seize compounds, thread-locking fluids, gasket sealants | Yes |
| Primary service | Process fluid, lubricants, fuel, hydraulic fluid | Usually addressed |
| Routine maintenance | Cleaning agents, degreasers, IPA, ammonia-based cleaners | Partially — cleaning agent brand matters |
| Emergency cleaning | Industrial solvents, strong disinfectants | Usually missed |
| Storage / transport | Packaging materials, anti-corrosion wraps, humidity | Usually missed |
6.2 Chemical Compatibility Reference for Polycarbonate
| Chemical / agent | Compatibility | ESC risk | Engineering action |
|---|---|---|---|
| Water (ambient temperature) | Good | Low | No action required |
| Dilute acids (pH > 3) | Good | Low | Monitor concentration |
| Dilute alkalis (pH < 11) | Moderate | Moderate | Test at application temperature and concentration |
| Strong alkalis | Poor | High | Change material or apply chemical-resistant coating |
| Aliphatic hydrocarbons (hexane, mineral spirits) | Good | Low | Standard use acceptable |
| Aromatic hydrocarbons (toluene, xylene) | Poor | Very high | Incompatible — do not use |
| Ketones (acetone, MEK) | Poor | Very high | Incompatible — do not use for cleaning |
| Esters (ethyl acetate) | Poor | High | Avoid |
| Isopropyl alcohol (IPA) < 30% | Moderate | Moderate | Acceptable if residual stress is low and contact time is brief |
| Isopropyl alcohol (IPA) > 30% | Poor | High | High risk if part has residual moulding stress |
| Ammonia-based cleaners | Poor | High | Substitue with compatible cleaner or apply hard coat |
| Silicone oils and greases | Good | Low | Acceptable |
| Mineral oils and greases | Good | Low | Acceptable |
| Most sunscreens (oxybenzone-containing) | Poor | High | Relevant for consumer products; specify coating if contact possible |
Procurement action: Do not accept “PC is compatible with IPA” as a blanket statement from a supplier. The answer depends on IPA concentration, part residual stress state, temperature, and contact duration. Require a written chemical compatibility statement against your specific service chemicals.
7. PC vs. Alternative Engineering Polymers: Comparative Durability
Polycarbonate is not always the optimal choice. The table below allows engineering teams to evaluate alternatives against the specific failure modes that drive end-of-life in their application.
Table 2: Comparative Engineering Polymer Durability Matrix
| Material | Impact resistance | UV stability | Max service temp (continuous) | Chemical resistance | Transparency | Outdoor lifespan estimate | Cost index | Best substitution case for PC |
|---|---|---|---|---|---|---|---|---|
| Polycarbonate (PC) | Excellent | Moderate (with UV coat: good) | ~120°C | Moderate (ESC risk) | Excellent | 10–15 yrs (UV coated) | Medium | — |
| Acrylic (PMMA) | Poor–Moderate | Excellent (inherent) | ~85–90°C | Good (few ESC risks) | Excellent (better than PC) | 15–20+ yrs | Low–Medium | When UV stability and optical clarity outweigh impact requirement |
| ASA (Acrylonitrile-Styrene-Acrylate) | Good | Excellent (inherent) | ~90°C | Good | Opaque only | 15–20 yrs | Low–Medium | Outdoor structural (opaque) housing; replaces ABS or opaque PC |
| ABS | Moderate | Poor | ~80°C | Moderate | Opaque | 3–7 yrs | Low | Not a durability upgrade from PC |
| PETG | Moderate | Poor–Moderate | ~70°C | Good | Good | 5–8 yrs | Low | Not suitable for demanding outdoor or thermal applications |
| PEI (Ultem) | Good | Good | ~170°C | Excellent | Amber tint | 20+ yrs | High | High-temperature electrical/aerospace where PC thermal limit insufficient |
| PEEK | Excellent | Excellent | ~250°C | Excellent | Opaque | 20+ yrs | Very high | Severe chemical + thermal environment where PC fails; justify cost vs. requirement |
| PTFE | Moderate | Excellent | ~260°C | Outstanding | Opaque | 20+ yrs | High | Chemical seals, linings; not a structural transparent replacement |
| Polysulfone (PSU) | Good | Moderate | ~160°C | Good (better than PC vs alkalis) | Good (amber tint) | 15+ yrs (indoor) | High | Medical sterilisation; elevated temperature; autoclave compatibility |
Decision logic for common scenarios:
| Scenario | Recommended material | Reason |
|---|---|---|
| Outdoor glazing, high impact possible | UV-stabilised PC + hard coat | Best impact/UV balance with coating |
| Outdoor signage, no impact risk | PMMA | Superior UV stability; lower cost |
| High-temperature electrical enclosure | PEI or PC heat-stabilised grade | Thermal headroom beyond PC standard Tg |
| Severe chemical exposure (ketones, esters) | PEEK or PTFE | PC chemically incompatible |
| Medical device housing (autoclavable) | PSU or PEI | Autoclave temperature exceeds PC limit |
| Consumer product, outdoor, coloured (opaque) | ASA | Inherent UV stability without coating; lower cost |
8. Accelerated Aging Testing: How to Validate Before You Commit
For applications in the bottom three rows of the lifespan matrix (Section 3), accelerated ageing testing should be a design validation requirement before committing to volume production — not an afterthought if field failures occur.
8.1 Standard Test Methods for Polycarbonate Durability Validation
| Test standard | What it simulates | What it measures | When to specify |
|---|---|---|---|
| ISO 4892-2 (Xenon arc) | Solar UV + temperature + humidity cycling | ΔE colour shift; gloss retention; impact strength retained after exposure | Outdoor or UV-exposed applications |
| ISO 4892-3 (UV fluorescent lamp) | UV-B heavy exposure | Yellowing index; molecular weight retention | Accelerated screening for UV degradation rate |
| IEC 60068-2-14 (thermal shock) | Rapid temperature cycling | Dimensional stability; crazing; delamination of coatings | Applications with wide temperature swings |
| ISO 22088-3 (ESC test) | Chemical contact under defined strain | Strain at failure in contact with test chemical; F50 ESC value | Any application with chemical exposure |
| ISO 175 (immersion chemical resistance) | Prolonged chemical immersion | Weight change; dimensional change; mechanical property retention | Fluid containment; prolonged chemical contact |
| IEC 60068-2-78 (damp heat) | Combined humidity and elevated temperature | Surface degradation; hydrolysis; adhesion of coatings | Tropical, marine, or high-humidity environments |
8.2 Reading Accelerated Aging Results: What to Accept and What to Reject
Accelerated ageing tests compress real-world time — but the acceleration factor is material- and condition-specific. Use these benchmarks as engineering guidance:
Xenon arc (ISO 4892-2) acceptance criteria for outdoor PC:
| Parameter | Acceptable result (after 1,000 hours Xenon) | Reject criterion |
|---|---|---|
| Colour shift (ΔE) | ≤ 3.0 | > 5.0 |
| Gloss retention | ≥ 60% of initial | < 40% |
| Impact strength retention | ≥ 60% of unaged value | < 50% |
| Coating adhesion (if coated) | Cross-cut test grade 0–1 (ISO 2409) | Grade ≥ 2 (cohesive or adhesive failure) |
ESC testing (ISO 22088-3) acceptance:
- Test at the maximum residual stress expected from your moulding process (or specify a minimum annealing cycle to reduce stress to the tested level)
- Pass criterion: no crack initiation within the exposure time corresponding to the specified service interval
- If F50 (strain at 50% specimen failure) is below the expected service strain, disqualify the material/chemical combination
9. Specifying Polycarbonate Components: What to Put in Your Drawing and RFQ
A drawing that says “Polycarbonate — translucent” is an incomplete specification for any precision engineering component. The following fields are required for a defensible specification.
9.1 Drawing / Technical Specification Requirements
Material specification block:
| Field | Example specification | Why it matters |
|---|---|---|
| Polymer base | Polycarbonate (PC) | Confirms base material |
| Grade designation | Makrolon 2605 UV or equivalent approved | Specifies additive package |
| UV stabilisation | Required — UV-stabilised grade mandatory | Prevents optical-grade substitution |
| Colour / clarity | Natural (water-clear); transmission ≥ 88% at 3mm | Prevents tinted or cloudy grade substitution |
| Flame classification | UL 94 V-0 at 3.0 mm (if applicable) | Required for electrical enclosures |
| Regulatory compliance | RoHS compliant; FDA CFR 21 Part 177.1580 (if food/medical) | Regulatory requirement |
| Material certificate | EN 10204 2.2 or 3.1 equivalent polymer cert required | Batch traceability |
Processing specification block:
| Field | Example specification | Why it matters |
|---|---|---|
| Moulding process | Injection moulding; process record retained | Ensures documented process |
| Post-moulding annealing | 125°C ± 5°C for 2 hours minimum; air-circulating oven | Controls residual stress |
| Surface finish | Injection: Ra ≤ 0.8 µm on optical faces; CNC machined: Ra ≤ 0.4 µm after polishing | Defines optical and tribological quality |
| Coating | Siloxane hard coat, minimum 3–5 µm; adhesion test to ISO 2409 grade ≤ 1 | Defines UV and scratch protection |
| Residual stress inspection | Polarised light birefringence check on first article | Validates annealing effectiveness |
Critical dimensions and tolerances:
For precision moulded PC, achievable tolerances depend on geometry and wall thickness. Use these working values:
| Feature | Achievable tolerance | Notes |
|---|---|---|
| Linear dimensions (< 100 mm) | ±0.10–0.20 mm | Moulded; varies with wall thickness and shrinkage |
| Linear dimensions (CNC machined) | ±0.02–0.05 mm | Significantly tighter than moulded |
| Angular | ±0.5° | Moulded; ±0.1° machined |
| Flatness (large faces) | 0.1–0.3 mm over 200 mm | Moulded; depends on cooling and annealing |
| Surface roughness (optical face) | Ra ≤ 0.4–0.8 µm | Post-polishing |
| Transmission (optical clarity) | ≥ 88% at specified thickness | Measured per ISO 13468 |
| Haze | ≤ 1.5% | Measured per ISO 14782 |
10. Supplier Qualification Checklist for Precision Polycarbonate Components
Use this checklist before placing a first production order with a polycarbonate precision parts supplier.
Technical Capability
- Supplier has confirmed grade stocking or procurement capability for your specified grade (not “general PC”)
- Supplier has documented moulding process capability: injection pressure, melt temperature, mould temperature, cooling time are controlled parameters
- Supplier performs post-moulding annealing and can provide time/temperature records
- Supplier has polarised light birefringence inspection capability for residual stress check
- Supplier has in-house optical measurement capability (transmission, haze) if optical clarity is a specification requirement
- Supplier can provide CMM or optical profilometer dimensional reports
- Supplier has coating capability or a qualified coating subcontractor if surface treatment is required
- Supplier can provide Cpk data on critical dimensional features
Quality Documentation
- ISO 9001 or IATF 16949 certificate provided (verify expiry date)
- Material certificate: polymer lot certificate with grade, batch number, and key properties (Melt Flow Rate, impact strength)
- First Article Inspection (FAI) report provided for all critical dimensions
- Accelerated ageing test data provided or agreed test programme confirmed for outdoor / chemical applications
- ESC chemical compatibility statement for specific chemicals in your operating environment
- Processing record available (injection moulding parameters and annealing cycle) — this is the evidence that residual stress has been managed
Red Flags — Investigate Further if Any Apply
- Supplier quotes “standard PC” without asking about application environment, UV exposure, or chemical exposure
- Supplier cannot provide a material lot certificate (only a generic datasheet)
With 8 years of experience in the engineering field, I possess a deep understanding of manufacturing processes and materials. Has helped more than 300 designers work together to develop prototypesAs the Project Manager at Modo Rapid, I directly liaise with designers and procurement teams, assisting designers in new product development, and helping to reduce development costs and time. From prototyping to mass production and market testing, I support developers throughout the entire process.
“My goal is to help developers get cost-effective prototypes and fast time-to-market to capture market share”.
